In 1943, Rhytidanthera mellifera was discovered on 
ancient (Cretaceous) sandstone hills in the Amazonian 
drainage of Colombia —a significant range extension. 
Although still confined within the boundaries of Colom- 
bia, Rhytidanthera had been located in the great Ama- 
zonian area, astonishingly distant from the eastern Cordil- 
lera. Furthermore, since the isolated sandstone hills of 
the Vaupés and Caqueta (where Rhytidanthera mellifera 
was collected) are remnant outliers of a once more or less 
continuous land-mass the core of which lies in southern 
Venezuela and British Guiana, the possibility of the dis- 
covery in the future of Rhytidanthera far to the east was 
open to suggestion. This curious distribution of Rhyti- 
danthera was accepted (Schultes in Bot. Mus. Leafl. 
Harvard Univ. 14 (1949) 84) as evidence for believing 
in an ancient migration or flow of Andean elements east- 
ward over the old Venezuelan-Guianan land-mass. 
The collection in the Macarena Mountains of Rhyti- 
danthera regalis stands out as one of the most significant 
phytogeographical discoveries of the last two decades. 
Both morphologically and geographically intermediate 
between the western species and the Amazonian Rhyti- 
danthera mellifera, the Macarena species provides us with 
an unexcelled ‘‘missing link.” 
Cotompra: Intendencia del Meta, Cordillera La Macarena (extremo 
nordeste), Macizo Renjifo, faldas orientales. Alt. 600-1300 m. ‘‘Tree 
60 ft. tall. Crown heavy. Flowers white, anthers yellow.’’ Decem- 
ber 30, 1950-January 5, 1951. Jesus M. Idrobo & Richard Evans 
Schultes 871 (Tyrer in Herb. Gray; Dupticarr tyre in Herb. Nac. 
Colomb. ).—Intendencia del Meta, Sierra de La Macarena, Central 
Mountains, North Ridge. Alt. 1500 m. “‘Dense forest. Tree up to 
15 m. high. Petals white ephemeral, stamens yellow, inclined to 
lower side of flower.’’? December 30, 1949, W. R. Philipson & J. M. 
Idrobo 2011.—Intendencia del Meta, Cordillera La Macarena (ex- 
tremo nordeste), Macizo Renjifo, faldas orientales. Alt. 600-1300 m. 
‘Tree growing on steep, rocky slopes. Height 60-70 feet. Diameter 
at base 20 inches. Bark dark reddish brown, slightly rough. Wood 
very hard. Usually somewhat gnarled. Fruit green.’’ December 30, 
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